Does iPhone have a Wi-Fi & Bluetooth toggle widget in Notification Center?
Solution 1:
You can toggle directly by swiping up from the very bottom of the screen…
...from the lock screen, home screen or in most apps [in some apps it's difficult to get the swipe to be recognised if the app uses the same part of the screen for a function.]
Solution 2:
It's not possible for a store-approved app to add a Notification Center widget as there are no public APIs for controlling Wi-Fi and Bluetooth power.
There might be private ones you could access with an app signed for enterprise or developer use, but using control center is a better idea for this.